Method of making ceramic dishware



Se t. 13, 1966 w. J. RECH 3,272,895

METHOD OF MAKING CERAMIC DISHWARE Original Filed Oct. 15, 1959 INVENTOR.

WILLIAM J. RECH ATTORNEYS United States Patent 3,272,895 METHOD OF MAKING CERAMIC DISHWARE William J. Rech, Neshannock Township, Lawrence County, Pa., assignor to Shenango Ceramics, Inc., New Castle, Pa., a corporation of Pennsylvania Original application Oct. 15, 1959, Ser. No. 846,571, now Patent No. 3,190,486, dated June 22, 1965. Divided and this application May 6, 1965, Ser. No. 453,650 4 Claims. (Cl. 26462) This application is a division of my copending application, Serial No. 846,571, filed October 15, 1959, now U.S. Patent No. 3,190,486, dated June 22, 1965.

This invention relates to a method of making platters, elongated vegetable bowls or dishes, olive dishes, and similar oval-shaped dishware having a central portion 'or well surrounded by a circumferential, upwardly sloping rim, and a supporting ridge or foot formed about the underside of the central portion. In particular, the invention relates to dishware of the type described which is manufactured from ceramic materials by conventional processes involving bisque and glost firing.

Elongated, oval-shaped dishware is customarily fired, as is round Ware, upside down in the bisque kiln with the rim and central portion supported either by a bed of flint sand carried on a refractory slab or by a refractory support known :as a crank. The purpose of firing the ware upside down while supporting the central portion is to maintain a straight rim and at the same time to prevent the central portion from dropping.

While the firing procedure described above does maintain a relatively straight aim, the foot of the ware frequently becomes distorted. The distortion of the foot may result from various single or cumulative causes. Either the sand may shift on the slab, or the slab or crank may warp during firing. Also, the ware itself, particularly at the ends of the oval foot, may grow, twist, or shrink unevenly during firing, possible due to the creation or relieving of internal stresses as the ceramic bond develops in the clay body, or simply to the non-uniform distribution of the mass of clay about a central point. The latter phenomenon may occur not only in the bisque firing of the ware, but in the glost firing as well.

Generally, the warping of the foot is not sufliciently aggravated and discernible as to cause the ware to be rejected. However, measures must be taken to correct the distortion since even a very slightly warped foot will cause the ware to rock when placed on a smooth, hard surface, such as a table top. Heretofore, the only solution has been to grind the foot flat, or at least to remove the major high spots after firing and glazing. This procedure adds to the cost of manufacture because of the time involved in grinding the extremely hard, vitrified ware and the relatively complex machinery which is required. Further, the ground unglazed surface of the foot tends to mar the surface of a lower platter in a stack of ware, as well as sometimes scratching the surface of atable.

The present invention solves the problem of foot distortion by providing a unique method of making the foot construction in which the ends of the oval foot are relieved before bisque firing the while the clay is in the green state. Even through other portions of the foot may still warp, the foot construction is such that a firm support will still be obtained without the necessity of grinding after firing and glazing.

Thus, the primary object of the invention is to provide a novel and improved method of making a non-rockable platter or similar ware. More specifically, it is an object of the invention to provide a novel and improved method of making a foot construction for elongated, oval-shaped 3,272,895 Patented Sept. 13, 1966 ware which will provide a firm support for the ware without the necessity of grinding the foot after firing.

Another object of the invention is to provide a novel method of making a foot construction for dishware which permits air to circulate beneath the central portion within the area encompassed by the foot, the circulation serving to lessen condensation on and under the foot of such dishware as well as minimizing the marring of table surfaces.

Other objects and attendant advantages of the invention will become readily apparent as the same becomes better understood when considered in reference to the fol-lowing detailed description and the accompanying drawing wherein:

FIGURE 1 is a vertical sectional view taken along the longitudinal center line of a platter made according to the method of my invention.

FIGURE 2 is a transverse vertical sectional view taken along the line 22 of FIG. 1 looking in the direction of the arrows. 1

FIGURE 3 is a bottom perspective view of the platter of FIGS. 1 and 32, showing the bottom and foot construction.

Referring in detail to FIGURES 1 and 2, there is shown a platter having a main central portion or well 10 surrounded by a conventional annular rim 11. The bottom of the central portion 10 is shaped to provide a conventional foot 12. If the ware is formed by conventional jiggering, pressing, or casting processes, initially the foot 12 will be a continuous ridge surrounding the underside of the central portion 10.

As previously stated, the construction of a platter or the like made according to this invention is such that it will normally provide a firm, non-rocking support for the platter without the necessity of subjecting the support to an expensive grinding operation. To this end, in accordance with the present method, the ends of the conventionally oval-shaped foot 12 are relieved before the ware is subjected to the initial bisque fire (i.e., while the ware is in a green state). If the ware is formed in a green state by the conventional processes mentioned above, in accordance with the present invention, the continuous, elliptical foot 12 preferably and most simply is relieved by cutting away or pressing down the ends of the foot 12 while the green ware is in the soft or moist plastic state and before it is dried prior to firing. This takes but a moment of the operators time and provides depressions 13 (when viewing the piece with the normal underside uppermost). The extent of the depressions 13 in the foot ridge 12 may vary according to size and elongation of the ridge 12 as the skill of the art dictates. As indicated in FIG. 2, each depression 13 is preferably located symmetrically about the longitudinal axis or center line of the piece and preferably slopes rather gradually toward the original surface of the foot 12, the longitudinally opposed depressions 13 dividing the portion of the foot 12 which is adapted to contact a planar surface, such as a table top, into two spaced and symmetrically opposed arcuate bearing surfaces or rib feet 14. Although the extent of the non-bearing, relieved portions 13 of the foot may vary, the length of a non-bearing depression 13 should be substantially less than the length of a bearing portion 14, as indicated in FIG. 2 by the projected length A of a depression 13 and in FIG. 1 by the projected length B of a bearing portion 14.

Instead of cutting or pressing down the depression 13 while the clay is in a soft, plastic state, the depressions may, in accordance with the present method, be formed by cutting, rubbing, or breaking away portions of the foot after drying and while the green ware is in the leather-hard state, the depressions 13 thus formed being smoothed by sponging during the fettling operations preparatory to firing. Formation of the depress-ions at this stage before firing may require slightly more time and care than formation while the ware is still plastic, but

it eliminates the performance of the operation on ware which may develop drying cracks and, thus, may be discarded. Alternatively, in accordance with the present invention, if the Ware is formed by casting or pressing, the mold grooves normally forming the foot may be filled in at the location of the depressions to shape the same in the course of forming the ware. Either of these latter two alternative procedures for forming the depressions 13 is indicated when the ware is formed by drypressing.

The geometry afforded by this construction is such that the platter will rest solidly on opposed arcuate surfaces of the rib feet 14 if no warping occurs, or if the ware warps only at the end portions encompassed within or beyond the area subtended by the arc of each depression 13. In the event either or both of the bearing surfaces or rib feet 14 are warped during a fire, it has been discovered that in almost all instances the ware still has a stable bearing support consisting either of (a) an arcuate line support provided by one bearing portion 14 and a plurality of spaced bearing areas on the opposite portion 14 which lie in the same plane as the arcuate foot portion, or (b), as a practical minimum, two pairs of spaced contact areas, all lying in the same plane with each contact area of a foot portion 14 being adjacent a depression 13.

It will be observed that at least four-point surface contact is necessary to stabilize the oval-shaped platter since the geometry is such that any three-point support would define a triangle having too small an area with respect to the well area to provide proper stability in use. That is, while a three-point support consisting of two points on one side of the center line of the piece of ware and one point on the other side of the piece of ware will allow the platter to rest in a fixed position, there will be a substantial outboard area, so to speak, of the well which is not included within the triangle defined by the three points. In use, therefore, any substantial pressure in that outboard area of the well 10 (as while carving meat, for example) will cause the platter to rock or tip. In the unusual event that ware embodying a foot constructed in accordance with the method of this invention warps so badly as to provide a three-point or two-point support (as when the centers of both arcuate surfaces 14 would be high), the whole piece would normally be so warped as to cause rejection without regard to whether or not it rocked on its foot.

The present method of providing the spaced feet or pedestal ribs 14 produces an advantage in addition to that of eliminating the conventional grinding operation. It will be observed that, when the platter is in its normal, right-side-up position, as shown in the drawing, the depressions or relieved portions 13 of the foot become openings allowing air to circulate between the well 10 and the table surface beneath it. This minimizes the sweating commonly occurring when there is a substantial temperature difierence between the ware and a flat surface on which it is placed and also facilitates the cooling of the table top area beneath the well when the ware is heated, thereby reducing the likelihood of marring a varnished table top, for example.

It is to be noted from the drawing that the ratio of the projected length of an arcuate rib 14 on the longitudinal center line of the platter to the length of the longitudinal center line is substantially greater than the ratio of the arcuate length of a space between the ribs 14 and the arcuate length of a rib. Thus, the non-rocking arcuate feet of ware made according to this invention, while substantially avoiding the possibility of rocking inherent in platters having an elliptical foot, afford a longitudinal support which is only negligibly shortened from that provided by a conventional elliptical foot, and the extent of lateral support is not decreased at all.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the method of the present invention, and that it is intended to cover all changes and modifications of the embodiments herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. In the method of making vitrified ceramic elongated ware adapted to be stable in use on a horizontal planar surface, by means of spaced arcuate feet symmetrically disposed with respect to the longitudinal center line of the ware, comprising the steps of forming said ware in a green state, firing, and glazing the same, the steps of forming said ware with a continuous elliptical foot and eliminating end portions of said foot prior to firing.

2. The method of claim 1 in which said ware is formed of wet clay in a plastic condition, the clay is dried prior to firing, and the step of eliminating said end portion of the foot is performed prior to drying.

3. The method of claim 1 in which said ware is formed of wet clay, the clay is dried and fettled preparatory to firing, and the step of eliminating said end portions of the foot is performed after drying and during the course of fettling said ware.

4. The method of claim 1 in which said foot is formed as a rib surrounding the central well portion and two end portions thereof are cut away to leave a pair of opposed arcuate feet extending along a major portion of the langitudinal centerline of said well and being substantially symmetrically disposed with respect to a transverse centerline of said well.

References Cited by the Examiner UNITED STATES PATENTS 1,984,108 12/1934 Bahl 264-162 XR 2,490,049 12/1949 Greger 26462 FOREIGN PATENTS 23,516 11/ 1908 Great Britain.

ROBERT F. WHITE, Primdry Examiner.

J. A. FINLAYSON, Assistant Examiner. 

1. IN THE METHOD OF MAKING VITRIFIED CERAMIC ELONGATED WARE ADAPTED TO BE STABLE IN USE ON A HORIZONTAL PLANAR SURFACE, BY MEANS OF SPACED ACURATE FEET SYMMETRICALLY DISPOSED WITH RESPECT TO THE LONGITUDINAL CENTRE LINE OF THE WARE, COMPRISING THE STEPS OF FORMING SAID WARE IN A GREEN STATE, FIRING, AND GLAZING THE SAME, THE STEPS OF FORMING SAID WARE WITH A CONTINUOUS ELLIPTICAL FOOT AND ELIMINATING END PORTIONS OF SAID FOOT PRIOR TO FIRING. 